This application claims the benefit of the Korean Application No. P2002-18269 filed on Apr. 3, 2002, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a backlight device, and more particularly, to a backlight device in a liquid crystal display device.
2. Discussion of the Related Art
Generally, a CRT (cathode ray tube) as one of the display devices as widely used is mainly applied as a monitor for a TV, a measuring device, an information terminal, or the like. However, the weight and size of CRT devices fail to cope with the demand for compact and light electronic devices.
As substitutions for such CRT""s, there can be mentioned a liquid crystal display (LCD) using the optical effect of an electrical field, a plasma display panel (PDP) using a gas electrical discharge, an electroluminescent display (ELD) using electroluminescence, and the like.
Thus, substantial effort has been made to study and develop the liquid crystal display device.
Lately, a flat liquid crystal display device having a display screen just several centimeters thick has been developed to be used as a monitor for space craft, for an airplane, as a notebook computer, a lap-top computer, a desk-top computer, a large-sized information display, or the like. Thus, demands for the liquid crystal display device continuously increase.
The liquid crystal display device is a light-receiving device displaying an image by controlling the quantity of light, thereby requiring an additional light source, i.e. a backlight device necessary for applying light to an LCD panel.
Backlight devices currently used include an EL (electroluminescent) backlight device, an LED backlight device, a CCFL (cold cathode fluorescent lamp) backlight device, and the like. The CCFL backlight device has less power consumption, provides a very bright white light, and has a small thickness. Hence, the CCFL backlight device is preferred to others.
The CCFL backlight device uses a direct or edge-light system and substantial effort has been made to study the edge-light system so as to cope with the demand for a thin and light-weighing display unit.
A backlight device for a monitor fabricated by a general edge-light system is explained as follows.
A backlight device for a general monitor, as shown in FIG. 1, includes a lamp 10 as a light sources emitting light, supported in frame 15, a light-guiding plate 11 guiding the light emitted from the lamp 10, a diffusion sheet 12 diffusing the light projected from the light-guiding plate 11 at a predetermined angle, a prism sheet 13 condensing the light diffusing from the diffusion sheet 12 so as to transfer the condensed light to an LCD panel unit 14, an LCD panel unit 14 on the prism sheet 13, a fixing mechanism (not shown in the drawing) under the light-guiding plate 11, and a reflection sheet 16 for reflecting the light transferred to the fixing mechanism on the LCD panel unit 14.
The backlight device further includes a lamp reflection sheet 18 disposed around the lamp 10 so as to reduce the loss of light projected from the lamp 10 and lamp holders 17 formed at both ends of the lamp 10 so as to fix the lamp 10 thereto as well as prevent contact between the light-guiding plate 11 and the lamp 10.
Two species of backlight devices according to the related art can be explained by referring to the attached drawings as follows.
A first backlight device according to related art, as shown in FIGS. 2A and 2B, includes a reflection sheet 23 beneath a light-guiding plate 21, a lamp reflection sheet 24 circumferential wrapping around the lamp 22, supported in lamp holder 26 and a fixing mechanism 25 which partially wraps around the lamp reflection sheet 24.
A second backlight device according to the related art, as shown in FIGS. 3A and 3B, includes a bottom reflection sheet 33 completely wrapping around the exterior of a lamp 32, supported a lamp holder 35 except for the light-incident face of a light-guiding plate 31 so as to carry out the function of a lamp reflection sheet. In this case, the fixing mechanism 34 is constituted so as to surround a lower portion and one side of the bottom reflection sheet 32.
The lamp reflection sheet 24 and the bottom reflection sheets 23 and 33 are made of materials having high reflectivity. In order to increase the reflective efficiency, metal is coated on the lamp reflection sheet 24 or a coating film is attached to the lamp reflection sheet 24. The bottom reflection sheets 23 and 33 are made of thin materials which bring about mirror reflection or diffusion reflection.
However, the structure of each of the backlight devices according to the related art becomes complicated due to the lamp reflection sheet 24 surrounding the lamp 32.
Moreover, when the bottom reflection sheet 33 extending for the function of a lamp reflection sheet is used, it is difficult to maintain the uniform shape to surround the lamp 32 since the bottom reflection sheet 33 is formed with a thin film.
The present invention is directed to a backlight device that substantially obviates one or more problems due to limitations and disadvantages of the related art.
Accordingly, an object of the present invention is to provide a backlight device which provided for light to be incident on a light-guiding plate without loss of the light generated from a lamp while at the same time simplifying the constitution of the backlight device.
Another object of the present invention is to provide a backlight device which stably fixes and protects the light-guiding plate and lamp.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, the backlight device of the present invention includes at least one lamp, a light-guiding plate for laterally receiving light emitted from the lamp and transferring the received light to an upper face, and a fixing mechanism surrounding the lamp and light-guiding plate for reflecting the light of the lamp toward the light-guiding plate, the fixing mechanism having at least one protrusion formed at an inner surface thereof.
Advantageously, the fixing mechanism is made of a material having a reflective function. More preferably, the fixing mechanism is made of a plastic material, e.g., a polyester or acrylic material. Also, a sheet or a film can be attached to or coated on the inner surface of the fixing mechanism which advantageously surrounds the entire lower face and a portion of the upper face of the light-guiding plate.
A protrusion can be located between the lamp and light-guiding plate for separating the lamp and light-guiding plate from each other. The light-guiding plate has a corresponding recess to accommodate to the protrusion for separating the lamps from the light-guiding plate.
The protrusion corresponding to the recess can be an uneven shape.
The lamp can be arranged at one side of the light-guiding plate or at both sides of the light-guiding plate. Preferably, the backlight device further includes lamp holders provided at both ends of the lamp for fixing the lamp in a predetermined position.
In another aspect of the present invention, the backlight device includes at least one lamp, a light-guiding plate for receiving light emitted from the lamp through a lateral face and transferring the received light to an upper face, a reflection sheet placed under the light-guiding plate and extending around the lamp so as to reflect the light of the lamp toward the light-guiding plate, and a fixing mechanism surrounding the light-guiding plate and reflection sheet, the fixing mechanism having at least one protrusion formed at an inner surface thereof. Preferably, the protrusion is placed between the lamp and light-guiding plate and the reflection sheet has a recess corresponding to the protrusion.
Preferably, the reflection sheet has a thickness equal to or less than 1 mm and is made of a plastic material such as polyester.
The light-guiding plate can also be provided with a recess which defines an area where the lamp can be inserted. Correspondingly, the fixing mechanism contains a protrusion which extends into the recess. Advantageously, the lamp is arranged at one side of the light-guiding plate or at both sides of the light-guiding plate. The backlight device further can include lamp holders formed at both ends of the lamp for fixing the lamp in a predetermined position.
In the above-constituted backlight devices, according to the present invention, the protrusion or uneven protruding portion are formed on the fixing mechanism so as to fix the light-guiding plate thereto without additionally forming a lamp reflection sheet. The backlight devices according to the present invention, using the edge-light system, are applicable to a monitor backlight device having lamps arranged at both sides of the light-guiding plate and a notebook computer backlight device having a lamp arranged on only one side of the light-guiding plate.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.